The present invention relates generally to a current detection method for a converter, and particularly to a current detection method for a direct-current (DC) to three-phase alternating-current (AC) converter. The method can utilize only a single DC sensor to detect and calculate the three-phase alternating currents.
Conventional converters typically have protection means for detecting over-current and over-load conditions, and for protecting the converters from damage when such conditions occur. In conventional DC to three-phase AC converters, a DC sensor and two AC sensors have to be used in order to detect the over-current and three-phase alternating currents respectively. With reference to FIG. 1, the basic circuit of a general DC to three-phase AC converter is shown. As shown in the drawing, the converter converts a DC source E into three-phase alternating currents T, S, and R which are then connected to a load (not shown), such as an induction motor. The basic circuit includes six transistors Q.sub.1 to Q.sub.6, and a driver 10 controlling the ON/OFF states of the transistors Q.sub.1 to Q.sub.6 to achieve the conversion purpose. The basic circuit further must include a DC sensor 14 for detecting the over-current to actuate a control device 12 to protect the converter, and two AC sensors 16 and 18 to detect the load currents. The sensors 14, 16, and 18 are very expensive, and thus comprise a large part of the cost of the converter.